1. Field of the Invention
The present invention relates to a spread illuminating apparatus of side light type in which a light source is arranged at a side surface (light entrance surface) of a light guide plate, and more specifically to a spread illuminating apparatus in which a plurality of point light sources are arranged in a plurality of rows along a side surface of a light guide plate.
2. Description of the Related Art
A side light type spread illuminating apparatus is advantageous in reducing the profile dimension and therefore is widely used as a lighting means for a liquid crystal display (LCD) panel particularly in small portable information devices such as cell-phones. A light emitting diode (LED), which is a point light source and highly environmentally compatible, is widely used as a light source arranged at a side surface of a light guide plate.
Recently, in order to keep up with the ever refining definition and enhancing performance of the LCD panel, it is requested to further increase the brightness of such a spread illuminating apparatus. A side light type spread illuminating apparatus is disclosed in which a plurality of LEDs are arranged in a plurality of rows at a side surface of a light guide plate so as to improve the brightness (refer to, for example, Japanese Patent Application Laid-Open No. 2007-73399).
FIG. 4 indicates an illumination apparatus 50 disclosed in Japanese Patent Application Laid-Open No. 2007-73399. The illumination apparatus 50 includes a light guide plate 51 having a rectangular shape and a plurality of LEDs 52 arranged at one side surface of the light guide plate 51. The one side surface of the light guide plate 51 includes a plurality of recesses 53 and a plurality of protrusions 54, which are arranged alternately so as to form a rectangular wave shape as a whole, and the LEDs 52 are arranged individually at the recesses 53 and the protrusions 54, specifically such that the LEDs 52 are arrayed in two straight rows so as to form a zigzag arrangement. A pair of terminals 52a are disposed on the respective sides of each of the LEDs 52 and soldered at a terminal (not shown) of a flexible printed board 55.
When a plurality of LEDs are disposed in a zigzag manner as described above, as many LEDs as possible can be accommodated without contact of neighboring terminals each disposed on the side of two adjacent LEDs, and a spread illuminating apparatus with a high brightness can be realized. However, it is ever and constantly requested to increase the brightness of a spread illuminating apparatus. Especially, it is strongly requested to develop a spread illuminating apparatus which can accommodate as many LEDs as possible so that one spread illuminating apparatus can emit two or more kinds of lights having respective different wavelength characteristics.